Synthetic Inorganic Chemistry

FERROUS AMMONIUM SULPHATE^343

Procedure: Measure 222 cc. of 6N H2SO4 into a 500-cc. flask,
and add 40 grams of iron filings in small portions. Shake the
mixture after each addition, and do not add a second portion until
the vigorous effervescence has begun to slacken. When all the
iron has been added, set the flask on the hot plate and let it stand
until no further reaction takes place. Allow the solution to cool,
and add cautiously 5 grams of ferrous carbonate. Shake the mix-
ture, and after 5 minutes again add 5 grams of ferrous carbonate.
Heat the mixture to boiling. The free acid should be completely
exhausted, and the solution should contain 2/3 F.W. FeSC>4.
Filter the hot solution and divide it into two equal portions. Use
one for preparing ferrous ammonium sulphate, and the other for
preparing ferric ammonium alum.

FERROUS AMMONIUM SULPHATE
To one portion of the ferrous sulphate solution add 45 grams of
ammonium sulphate and 5 cc. of 6 N H2SO4. From the solubility
data given below determine the volume of solution required to
crystallize ferrous ammonium sulphate. (Note that the data are
for anhydrous salts.) After your instructor has checked your
result, adjust the volume to the proper value. Filter the solution
if it is not clear, and allow it to stand in a crystallizing dish until
a satisfactory yield of the double salt has formed. Decant the
mother liquor from the crystals, and wash them with a little dis-
tilled water. Dry them thoroughly at room temperature with
white paper towels.

Test the finished product for ferric iron, by dissolving a little in
water, adding a drop of 6 N H2SO4 and a few drops of KSCN. A
red color indicates ferric iron.

A saturated solution contains for each 100 grams of water the given

number of grams of the anhydrous salt.

Temperature
FeSO 4
(NH 4 ) 2 SO 4
FeSO4-(NH 4 ) 2 SO4...

0°

16

71

12

10°

21

73

17

20°

26

75

22

30°

33

78

28

40°

44

81

33

50°

48

84

40

70°

56

92

52

90°

43

99